1. Field of the Invention
The invention relates to ships. More particularly, the invention relates to a ship-board life raft handling apparatus. Most particularly, the invention relates to an apparatus for launching a life raft from below-deck.
2. Discussion of the Related Art
U.S. naval vessels carry life boats or life rafts for the emergency evacuation of the crew. Life boats and life rafts are stored on deck and lowered to the sea by means of davits. Because a life raft is uninflated for storage, it takes up less space than a life boat and is often the preferred evacuation vessel. A life raft is stored on deck in the uninflated and folded state in a life raft canister and then inflated immediately before use. A canister allows the life raft to be dropped from deck into the sea which eliminates the need for davits. The life raft is deployed from the canister when the sea painter connected to the inflation system is pulled, actuating inflation valves. Included in the canister is inflation means such as an inflation gas cylinder attached to the folded life raft. The life boat canister is periodically opened and inspected for integrity of the life raft and for gas pressure in the inflation gas cylinder.
U.S. naval vessels typically carry life rafts in preference to life boats. Smaller vessels carry 6 to 15 person life rafts. Standard Navy life rafts are the 25-person Mark 7 (Mk-7) and the 50-person Mark 8 (Mk-8). These life rafts are made of polyurethane coated nylon fabric and are stored with a gas inflation cylinder in a life boat canister. The canister is a hard fiber glass shell. The Mark 7 raft takes 550 cubic inches of gas to inflate from an inflation cylinder at a minimum test pressure of 4500 psi (pounds per square inch). The Mark 8 raft takes 1636 cubic inches of gas to inflate from two inflation cylinders at a minimum test pressure of 3500 psi (pounds per square inch). The inflation cylinders have a 15 year service life and contain carbon dioxide, nitrogen or air. For human safety, air is the preferred gas. Air also demonstrates less contraction than carbon dioxide in arctic temperatures.
Life raft canisters are stored on a ship deck to facilitate rapid deployment overboard in an emergency. It is statistically unlikely that a ship will sink during its useful life, and require evacuation to save lives. For safety awareness, the crew is periodically drilled to maintain their skills in handling a life raft. Likewise, the life raft canister is periodically opened and inspected to assure that the raft is in good working order and the inflation gas cylinder is up to standard operating pressure.
Life raft drills are carried out to reduce the inherent danger and inefficiency inherent in a real evacuation. Accordingly, a naval ship carries an excess of life raft capacity over the nominal crew size to accommodate damaged equipment and deviations in distribution and timing during evacuation. Life raft canisters are given priority in taking up deck space. Other essential equipment claims remaining deck space. As a result there is a conflict for the use of deck space between carrying on a ship's sailing and military functions and storage of emergency equipment.